Rotational angle detecting apparatus

Abstract

A rotational angle detecting apparatus comprises a rotary disc having first protrusions for an angle signal provided along the outer periphery of the disc and second protrusion for a reference signal arranged adjacent to the first protrusions in the thickness direction of the disc. A pick-up assembly is disposed to face the second protrusion to sense the rotationl position thereof. The sensed signal including noise components due to a magnetic coupling between the pick-up assembly and the first protrusions is subject to an integration and then applied to a level detector to generate a first pulse signal which occurs only during the integration signal being greater than a predetermined threshold level. On the other hand, a second pulse signal is produced by shaping the sensed signal. The first and second pulse signals are applied to an AND logic gate from which an output pulse is obtained in synchronism with the rotation of the disc.

We claim: 
     
       1. A rotational angle detecting apparatus comprising: (a) a rotary disc having at least one protrusion provided at the periphery of the disc;   (b) a pick-up assembly for sensing a rotating position of the protrusion to produce an alternating signal in synchronism with the rotation of the disc;   (c) an integration circuit for producing an integration of the alternating signal with time;   (d) a level detector for sensing the integration signal thus obtained above a predetermined threshold level to produce a first rectangular wave signal occuring when the integration signal is over in level the predetermined threshold level;   (e) a polarity detector for sensing one of positive and negative polarities of the alternating signal to produce a second rectangular wave signal occuring when the alternating voltage is in the sensed polarity; and   (f) a logic circuit coupled to both the level detector and the polarity detector to receive the first and second rectangular wave signals for producing an AND logic signal therebetween.   
     
     
       2. A rotational angle detecting apparatus for controlling an internal combustion engine, comprising; (a) a rotary disc mounted on a crank shaft of the internal combustion engine to rotate in synchhronism therewith;   (b) first protrusions provided along anouter pehiphery of the disc with equally spaced relationship;   (c) second protrusion provided adjacent to the first protrusions in the thickness direction of the rotary disc at its periphery;   (d) first pick-up assembly for sensing a rotational position of the first protrusions to produce a first alternating voltage in accordance with the rotation of the disc;   (e) second pick-up assembly for sensing a rotational position of said second protrusion to produce a second alternating voltage in synchronism with the rotation of the disc;   (f) an integration circuit for producing an integration of the second alternating signal with time, the second alternating signal including noise components due to a magnetic coupling between the first protrusions and the second pick-up assembly;   (g) a level detector for sensing the integration signal obtained over a threshold level which is determined to be greater than said noise components to produce a first rectangular wave signal occuring only when the integration signal is over in level the threshold level;   (h) a waveform shaping circuit for producing a second rectangular wave signal by shaping the second alternating signal;   (i) circuit means coupled to receive the first and second rectangular wave signals for producing a signal which occurs only when both the first and second rectangular wave signals are received at the same time.   
     
     
       3. A rotational angle dectecting apparatus as defined in claim 2, wherein the first pick-up assemblies are arranged such that when one of the first pick-up assemblies is positioned to just face one of the first protrusions, the other one of the first pick-up assemblies is positioned to face with a predetermined phase difference to the other one of the first protrusions. 
     
     
       4. A rotational angle detecting apparatus as defined in claim 3, which further comprises first circuit means for shaping a first alternating voltage sensed by one of the first pick-up assemblies to produce a first pulse having the same phase as the first alternating voltage, second circuit means for shaping a second alternating voltage sensed by the other one of the first pick-up assemblies to produce a second pulse having a phase inverted relation with the second alternating voltage, first logic circuit for taking NOR logic between the first and second pulses, second logic circuit for taking AND logic between the first and second pulses and third logic circuit for taking OR logic between both the outputs of the first and second logic circuits to produce a rotational angle detection signal. 
     
     
       5. A rotational angle detecting apparatus as defined in claim 1, in which the integration circuit comprises a comparator having first and second input terminals and an output terminal, a signal sensed by the pick-up assembly being applied across the two input terminals, capacitor means connected between the first input terminal and the output terminal of the comparator and a circuit means for applying a predetermined D.C voltage to the first input terminal of the comparator. 
     
     
       6. A rotational angle detecting apparatus as defined in claim 1 or 2, in which the level detector comprises a pair of transistors, one of the transistors having a base to which an output of the integration circuit is applied, an emitter connected in common with an emitter of the other transistor and a collector to which a D.C voltage is applied and the other transistor having a base to which a predetermined bias potential is applied, a collector connected through a load to a supply of the D.C voltage. 
     
     
       7. A rotational angle detecting apparatus comprising: (a) a rotary disc having at least one protrusion provided at the periphery of the disc;   (b) a pick-up assembly for sensing a rotating position of the portrusion to produce an alternating signal in synchronism with the rotation of the disc;   (c) an integration circuit for producing an integration of the alternating signal with time;   (d) a circuit means connected with the integration circuit for detecting a peak value of an output signal of the integration circuit;   (e) a divider circuit means for dividing the peak value to produce a reference voltage;   (f) a comparator means connected to receive the reference voltage and the output of the integration circuit for generating a pulse signal which occurs when the output of the integration circuit is greater in level than the reference voltage;   (g) a waveform shaping circuit for producing a pulse signal by shaping the alternating signal sensed by the pick-up assembly; and   (h) a logic circuit means coupled to receive the pulse signals from the comparator means and the waveform shaping circuit means for producing an output signal which occurs only when both the pulse signals are received at the same time.   
     
     
       8. A rotational angle detecting apparatus as defined in claim 7, in which said circuit means for producing a peak value of the integration output comprises a transistor having a base, an emitter and a collector, a diode connected between the output of the integration circuit and the base of the transistor in such a direction that a potential at the base changes in response to the output of the comparator, and a capacitor connected across the emitter of the transistor and a common potential line. 
     
     
       9. A rotational angle detecting apparatus as defined in claim 8, wherein said comparator means has first input terminal to receive the output of the integration circuit and second input terminal to receive the reference voltage, and which further comprises a circuit means for applying a predetermined D.C voltage to the second input terminal of the comparator means.